Figure 4.

¹³C spectra of DA3 cells perfused with ¹³C₁ glucose, (a) Controls — cells were perfused with [¹³C₁]-glucose-enriched medium and ¹³C spectra were continuously recorded, (b) Following a complete washout for 60 minutes with normal medium, the cells were perfused with DMEM containing HGF/SF (100 ng/ml) for 60 minutes and the ¹³C NMR experiment was repeated on the same sample, (c) Following a second washout, the cells were perfused with DMEM containing 200 mM phloretin. For acquisition parameters, see Materials and Methods section; line broadening = 15 Hz. Each spectrum was accumulated for 4 hours and 40 minutes. The time scale starts at the point at which [¹³C₁]-glucose reached the cells. Note that lactate production and accumulation reached plateau in approximately 20 to 25 minutes. Chemical shifts were determined by standardizing glucose to 94.7 ppm. glc, glucose; lac, lactate; ref, reference (dioxane in a capillary). DMSO was used to dissolve phloretin (see Results section: ¹³C NMR). There are no lactate signals in the phloretin experiment.